LOS ANGELES -- At first glance, Alejandro Rosso and Jonas of Plastilina Mosh seemed small and alone on the stage of the Troubadour on Friday.

It was just two guys and their instruments.

The eclectic Mexican rock duo was opening the show for Canadian trip-pop group Esthero before a sold-out house. But one only needed to look at and listen to Plastilina Mosh for a few minutes to see they were far from alone, and anything but small.

Singer/guitarist Jonas' scraggly bleached hair was wild. He grinned and launched into the song "Pornoshop." His vocals alternated between Spanish and English throughout the set.

In a tan '60s bowling shirt and close-cropped hair, Rosso looked as if he could be Desi Arnaz's fresh-faced little brother on a lost episode of "I Love Lucy." Occasionally, he piped in vocals, but he was generally busy taking care of all the samples and keyboards.

A variety-pack of fans had filled the hot, damp club for this double-bill that crossed America's borders -- and a few musical borders as well. From the woman with soap-opera curls and a Chanel shoulder bag to the guy with waist-length dreadlocks, customers found a place in the club and stayed there.

Rosso and Jonas played most of their recently released debut album, Aquamosh, including "Monster Truck," with Jonas explaining, in slightly embarrassed English, that it's his favorite track. He managed the lyrics fine -- "I'm a monster truck/ And I can destroy you."

"Plastilina Mosh is a two-ton truck of fun!" giggled Sherri Fanning, 22, of Gardena, Calif. She held a rolled-up poster in her hand that she had just peeled off a wall at the club. "Viva La Mosh for sure!" Then she turned back toward the stage.

High-tech lights swept over the musicians, shining brightly colored stars and loops around the room. String samples swelled over a dull mumble of voices as the crowd's attention started to wander during the slower songs.

As the set came to a close, Rosso stepped out from behind the keyboards for "Savage Sucker Boy." The near-metal song spooled along fine without his keyboard help. But he returned to his post for the finale, the rocking "Mr. P. Mosh," which had some in the crowd shaking booty.

"They seemed a little disorganized at first," said Billy Palmier, 24, of Los Angeles. "But then, they got into it. The music sounded great."

About an hour passed, and the stage remained empty, except for a roadie strategically placing water bottles for the band. They were keeping it legal for Esthero -- the lead singer is not yet 21.

A cheer went up as Esthero finally appeared.

Esthero is the name of an ever-mutating band, featuring eight players on Friday, including a DJ and a second drummer with congas. Confusingly, Esthero is also the name of the girl who sings lead vocals. Her red hair was cropped short and unkempt and she wore a sleeveless shirt and low-slung skirt.

As young as she is, Esthero was professional. Her remarkable voice swooned over soft grooves that caressed the Troubadour.

He paused as they began a new song with a rhythm that stuttered and jammed forward. "Nice backbeat, though," Gonzales said.

Esthero, the singer, looked to her partner, guitarist/producer Doc, from time to time, as if she wanted him to step up and take some of the glory. But he just smiled at her and hung back. They swung through most of their first record, including "Breath From Another" (RealAudio excerpt) and "Swallow Me," sounding jazzy, cool, smooth and trippy.

The audience responded with enthusiasm. "I heard she's going to be the next Natalie Imbruglia," said a wide-eyed Janine Rush, 21, of Los Angeles.

Of course, the crowd really loved it when Esthero played their radio hit, "Heaven Sent" (RealAudio excerpt), which has been added to MTV's catalog as a "breakthrough video."

Esthero, the singer, didn't miss a note as the audience cheered. She came through as the consummate professional, holding her audience spellbound for much of the night.